In using dental glass ionomer cements, α-β unsaturated carboxylic acid polymers such as polycarboxylic acid, and fluoroaluminosilicate glass powders are allowed to react to each other to be hardened, in the presence of water. These dental glass ionomer cements are widely used in dentistry, because they have excellent characteristics, for example very good biocompatibility, excellent aesthetic property of semi-transparent hardened body, excellent adhesion to tooth substrates such as enamel and dentine, and an anticariogenic effect by fluoride contained in glass.
A general dental glass ionomer cement is formed from a powder component and a liquid component, and therefore has a demerit that its handling such as measuring and mixing are troublesome. The applicant of the present invention previously developed a glass ionomer cement composition in a paste form consisting of a first paste whose main components are an α-β unsaturated carboxylic acid polymer, water, and a filler that does not react with the α-β unsaturated carboxylic acid polymer, and a second paste whose main components are a fluoroaluminosilicate glass powder and a polymerizable monomer not having an acid group, wherein a polymerization initiator is mixed with at least either one of the pastes, depending on the polymerization method of the polymerizable monomer (see Patent Literature 1 for example).
However, the strength of a hardened body of the dental glass ionomer cement composition is insufficient. This is because the interaction between the filler that does not react with the α-β unsaturated carboxylic acid polymer and the base component of the cement (the α-β unsaturated carboxylic acid polymer and fluoroaluminosilicate glass) is weak.
Against this problem, a filler for dental materials including: a particle of feldspar or feldspar derivative coated by a silicon compound containing a reactive group; and a polymerizable resin that can react with the reactive group is disclosed (see Patent Literature 2 for example). However, the strength of a hardened body of this filler is insufficient, because the interaction of the filling material with main components of cement is weak. In addition, feldspar is a natural product, whose composition is inhomogeneous, and metal contained in feldspar easily elutes in the presence of water. As such, feldspar is not a suitable filling material for glass ionomer cements.
In order to solve this problem, suggested is a filler whose surface is treated with a polyacid selected from the group consisting of homopolymers and copolymers of acrylic acid, maleic acid, itaconic acid, methacrylic acid, and combinations thereof, and with aminoalkyltrialkoxysilane as a linking group (see Patent Literature 3 for example). However, this surface treatment tends to be troublesome and cost a lot, and has a problem that the surface easily gets uneven and a stable effect is difficult to be obtained.